Casting core fabricating apparatus comprises a mold sand feeder, a mold sand tank to be filled with a specified quantity of mold sand supplied by the feeder, a vehicle for lifting the tank when it was filled with a specified quantity of mold sand and moving it to a position confronting the mold for the core, and a mold sand charger for charging by force into the mold the mold sand from the tank in the position confronting the mold.
The mold sand charged into the mold is heated and the resin therein is cured, resulting in a completed casting core of a desired shape.
The mold sand tank, after charging the sand into the mold, is returned by the vehicle to the position confronting the mold sand feeder and the tank is filled again with a necessary quantity of mold sand for forming a core, and the same operation is repeated.
In this way, in every mold forming cycle, the mold sand tank is filled with mold sand, the entire mold sand in the tank is charged into the mold by the mold sand charger by forcing the sand by an air or other jet means, and then the core is heated and cured. Therefore the mold sand tank must be filled with a specific quantity of mold sand suited exactly to the volume charged into the mold in each cycle.
Conventionally, the supply of mold sand from the mold sand feeder into the mold sand tank is controlled by a timer. The time required to fill up the tank is usually predetermined by experience or calculation, to stop the supply of mold sand when reaching the present time.
In this conventional mold sand filling method, if the flow of the mold sand is slow due to the type of mold sand, humidity, ambient condition or the like, the actual quantity of sand charged into the tank can be smaller than specified, or if the flow of the mold sand is faster than necessary, then too much mold sand is charged into the tank. It was thus difficult to maintain the feed of mold sand at a reasonably constant level. Thus, the degree of consolidation of the fabricated core is not constant and this results in defective products.